6 1/2" woofer suggestions -- MTM

[jmar]

I want to build an MTM system using a couple of tweeters that I already have and like very much, Vifa D27TG-05.

I want a sealed system that I'll be using with a subwoofer.

For now, I don't want to be too picky with my design (I want it right, but perfection isn't a goal at the moment). I just need some damn speakers right now.

It looks like the Vifa is pretty flat from 2K up, it had an Fs of 950hz, 91db spl.

So what is a good typical crossover point? (I've seen anywhere from 3k to 3.5K, according to a google search).

Don't laugh, but for now, I think I'll just use a cap for a first order because eventually, I'll be using an active crossover.

So, can anyone suggest some woofers that would be a good match in an MTM arrangement with these?

I have my eye on some $25 Goldwood's but would like to hear about some other ideas -- can't spend too much. They don't need to be shielded (unless they should be in an MTM?) (Can the magnets influence each other that close?)

[MisterTwister]

if you are going to use just a cap for crossover, then you'll need polypropylene cone woofers. such as these Madisound 6102-8 6" Polypropylene Cone Woofer from Madisound
they breakup lower in frequency than paper or metal, but don't sound as offensive IMO.

[tinitus]

Originally Posted by jmar

can't spend too much.

If doing your own
The only way I see you have a chance is to choose a single VERY well behaved driver pr side
On a budget, and with subs, I would choose Eminence Beta-8A, which I think might suit your tweeter
And it may not need much crossover
A relatively small inductor to take the worst top off the Beta, and let it roll off by itself, and just a small cap on the tweeter, but carefully adjusted
It might work

[jmar]

One thing I need to ask about a 2 woofer mtm system --

what are the considerations for matching SPL when using a pair of woofers? do you still shoot for 91db on each (like the tweeter?).

also the tweeters are 6 ohms -- would you use (2) 8 ohm in parallel, or (2) 4 ohm in series?

I thought of (2) 4 ohm is series for the sake of my amplifier.

[Michael Chua]

I haven't tried the Goldwoods but I have two shielded Silver Flutes in MTM with the HiVi RT1C Planar in the middle. Loaded them in a 22L ported box. Though the bass is not as articulate as I would like, its not bass shy. Cross with an active sub at 70-80Hz and you will have a decent HT system. The W14RC25 are very good value for money.

Regards
Mike

[jmar]

those look pretty nice -- very flat past the crossover point. maybe I should be looking ar a smaller 5" like this for the higher frequency response.

want to ask again about SPL and dual woofers especially if they're in parallel or series (which they're BOUND to be).

don't think it makes any difference, does it? you just try to match all the drivers as close as you can, right?

woofer 1 91db
woofer 2 91db
vifa tweeter 91 db

[jmar]

well actually, with 2 woofers in parallel I would want a lower spl?

lower by how much?

is there a formula somewhere to get this result for parrallel or series connected speakers?

[TerryO]

Originally Posted by jmar

well actually, with 2 woofers in parallel I would want a lower spl?

lower by how much?

is there a formula somewhere to get this result for parrallel or series connected speakers?

jmar,

The rule of thumb is that if the 2 woofers are in parallel you divide by 2.
Example: 8 ohm drivers in parallel would be 4 ohms. (note that two woofers with 3.8 ohms would be 1.9 ohms...not a good figure for many amplifiers).

In series this is reversed and you would multiply by 2. So two 4 ohm woofers would be 8 ohms.

The problem with this is that drivers vary so much within their respective operating range and a 4 ohm nominal driver may dip quite a bit lower and really cause problems. You actually need to see the actual impedance curve to get an accurate idea of what you're up against, as the impedance can vary as much as 50 ohms and the nominal figure may simply be some sort of weighted average. IOW: Don't go by nominal figures.

Best Regards,
TerryO

[jmar]

I'm asking about how it effects your approach on SPL not how to calculate the impedance.

[MJL21193]

Originally Posted by jmar

I'm asking about how it effects your approach on SPL not how to calculate the impedance.

Adding another driver, regardless of how they are connected, will give 3db more for a given power input.